Storage of rocket motors and missiles in volume-limited enclosures such as silos, ground transporters, submarine launch tubes and space shuttle cargo bays or the like presents a problem of packaging the high expansion ratio nozzles needed to maximize altitude performance. Use of extendible exit nozzles enables storage of the engines with the extendible nozzles in the stowed position; thereby decreasing the required packaging volume. Upon deployment the extendible nozzle provides a high expansion ratio, high performance nozzle during engine operation.
As explained for example in my earlier U.S. Pat. No. 4,184,238, the nozzle expansion of a rocket engine required for maximum thrust efficiency varies with ambient pressure. In multi-stage rocket engines where a later stage is to be fired in space or at high altitudes, the expansion ratio is of major importance and requires a terminal divergent exit nozzle for the rocket engine of substantial length and exit diameter. However, to make a second or later engine stage of such overall length and diameter as would be required to produce a requisite expansion ratio, would be extremely cumbersome and wasteful of otherwise usable space in the rocket assembly. Thus, it is desirable to provide means associated with a rocket engine so that a divergent nozzle of a length and diameter suitable for maximum thrust at low ambient pressure may be obtained by deploying such means substantially coincidental to firing of the engine. In this way, the inoperative rocket engine and its accessories may be so compacted that the entire assembly requires a storage space no larger than the profile of the basic rocket engine component of the assembly. Whereas the prior art patents referred to hereinabove relate to this same problem, the present invention provides a still more efficient and effectively operating mechanism for the stated purpose.